What's the least expensive way to make calls on a BB when travelling internationally?

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My wife and I are going to be in Europe for a couple of weeks this summer, and I'm trying to figure out the least expensive way to make calls on my BB while we're in Europe.

AT&T has an international data package that gives me 20MB of data for $25. Although I'd be limited, that would be sufficient for receiving e-mail and some limited internet use.

However, the best deal they have for calls is a plan that costs $5.99/month, plus 99 cents per minute.

My BB is unlocked, so theoretically I could purchase an international SIM, but the international SIM will cost about $60 by itself, which would amount to 60 minutes of calls on the AT&T plan before I start saving any money. Plus, with an international SIM, I wouldn't receive my e-mail unless I kept swapping the SIMs back and forth.

Does anybody know of any alternatives to what I described above?

Ideally, I'd like a solution that enabled me to make calls while in Europe to other locations in Europe, and also back home to the US.